DESCRIPTION

The ASN1 object utility functions process ASN1_OBJECT structures which are
a representation of the ASN1OBJECTIDENTIFIER (OID) type.

OBJ_nid2obj(), OBJ_nid2ln() and OBJ_nid2sn() convert the NIDn to
an ASN1_OBJECT structure, its long name and its short name respectively,
or NULL is an error occurred.

OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() return the corresponding NID
for the object o, the long name <ln> or the short name <sn> respectively
or NID_undef if an error occurred.

OBJ_txt2nid() returns NID corresponding to text string <s>. s can be
a long name, a short name or the numerical respresentation of an object.

OBJ_txt2obj() converts the text string s into an ASN1_OBJECT structure.
If no_name is 0 then long names and short names will be interpreted
as well as numerical forms. If no_name is 1 only the numerical form
is acceptable.

OBJ_obj2txt() converts the ASN1_OBJECTa into a textual representation.
The representation is written as a null terminated string to buf
at most buf_len bytes are written, truncating the result if necessary.
The total amount of space required is returned. If no_name is 0 then
if the object has a long or short name then that will be used, otherwise
the numerical form will be used. If no_name is 1 then the numerical
form will always be used.

OBJ_cmp() compares a to b. If the two are identical 0 is returned.

OBJ_dup() returns a copy of o.

OBJ_create() adds a new object to the internal table. oid is the
numerical form of the object, sn the short name and ln the
long name. A new NID is returned for the created object.

OBJ_cleanup() cleans up OpenSSLs internal object table: this should
be called before an application exits if any new objects were added
using OBJ_create().

NOTES

Objects in OpenSSL can have a short name, a long name and a numerical
identifier (NID) associated with them. A standard set of objects is
represented in an internal table. The appropriate values are defined
in the header file objects.h.

Table objects have certain advantages over other objects: for example
their NIDs can be used in a C language switch statement. They are
also static constant structures which are shared: that is there
is only a single constant structure for each table object.

Objects which are not in the table have the NID value NID_undef.

Objects do not need to be in the internal tables to be processed,
the functions OBJ_txt2obj() and OBJ_obj2txt() can process the numerical
form of an OID.

BUGS

OBJ_obj2txt() is awkward and messy to use: it doesn't follow the
convention of other OpenSSL functions where the buffer can be set
to NULL to determine the amount of data that should be written.
Instead buf must point to a valid buffer and buf_len should
be set to a positive value. A buffer length of 80 should be more
than enough to handle any OID encountered in practice.

RETURN VALUES

OBJ_nid2obj() returns an ASN1_OBJECT structure or NULL is an
error occurred.

OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or NULL
on error.

OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return
a NID or NID_undef on error.